Torque sensor assembly for robotic arm actuator

Abstract

A robotic arm actuator comprising a stator assembly and a rotor assembly. A motor is between the stator assembly and the rotor assembly to impart a relative rotation between the stator assembly and the rotor assembly. The stator assembly or the rotor assembly has a casing shell connected to the motor and configured to be connected to a link, the casing shell defining a plurality of shear panels in a segment between the motor and the link for the plurality of the shear panels to be in a load path therebetween, and sensors on the shear panels configured to measure torque on the shear panels.

Description

TORQUE SENSOR ASSEMBLY FORROBOTIC ARM ACTUATOR CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the priority of United States Patent Application No. 63 / 788,415, filed on April 14, 2025 and incorporated herein by reference.TECHNICAL FIELD

[0002] The present application relates to robot arms or like articulated mechanisms and torque sensors therefor.BACKGROUND OF THE ART

[0003] Robotic arms are increasingly used in a number of different applications, from manufacturing, to servicing, and assistive robotics, among numerous possibilities. Serial robot arms are convenient in that they may cover wide working volumes. To ensure their precise control, serial robot arms are provided with torque sensors, with torque sensing capability, to monitor effectively actions being performed by the serial robot arms and for the robot arms to sense their environment.

[0004] In the context of a robotic arm, the torque sensor is commonly used to read only one physical effect: the torque applied on the axis of the actuator. When this reading is noisy / inaccurate, the robotic arm becomes more difficult to control, whether it is entirely controlled by its controller (control of the motors, collision detection, load applied by the robotic arm, etc.) or hand-guided at its end effector (the torque read from each actuator when an operator moves the arm allows the arm to have a smooth and precise movement) in a collaborative mode. The precise reading of the torque applied by each actuator, without interference from other loads, allows for a smooth and precise control of the robotic arm.

[0005] Commonly used “cup” style torque sensors (i.e., a cylindrical metallic piece on which strain gauges are glued onto), while compact and easily manufacturable, may not isolate all external forces and torques applied on a robotic arm actuator on the axes other than the actuator central axis. In other words, the torque sensor, meant to read only the torque applied along the axis of the actuator, may also be impacted by shear forces, axialloads and bending moments applied on the actuator. The higher these loads, the higher the error and noise on the torque readings.

[0006] The ideal torque sensor would only read the on-axis torque and be isolated from all other loads, provide redundancy and be relatively inexpensive to produce. While solutions are available such as a torque sensor integrated in the gear unit of the actuator or positioned in such a way that bending moments and shear loads do not reach it, such as between bearings, these solutions may be less compact, may add length to the actuator, or may be much more expensive to integrate and fabricate.

[0007] Furthermore, in the context of actuator development, the assembly of a torque sensor within the actuator can highly impact the torque sensor performance. For example, if the torque sensor is positioned downstream from the motor, the torque from the motor is not directly read by the torque sensor (typically 1 % of the actuator torque output, using 1 :100 gears). Moreover, the sealing strategy has an impact on the torque read: seals between the rotor and stator of the actuator may be in the torque path of the torque sensor, adding to the error. The torque error from the seals may be particularly visible when hand guiding the robot: the torque applied on the robot from the user must be higher that the torque from the seals to induce a movement, resulting occasionally in a jerky movement.SUMMARY

[0008] it is an aim of the present disclosure to provide a robot arm that addresses issues related to the prior art.

[0009] Therefore, in accordance with a first aspect of the present disclosure, there is provided a robotic arm actuator comprising: a stator assembly; a rotor assembly; and a motor between the stator assembly and the rotor assembly to impart a relative rotation between the stator assembly and the rotor assembly; wherein the stator assembly or the rotor assembly has a casing shell connected to the motor and configured to be connected to a link, the casing shell defining a plurality of shear panels in a segment between the motor and the link for the plurality of the shear panels to be in a load path therebetween, and sensors on the shear panels configured to measure torque on the shear panels.

[0010] Further in accordance with the first aspect, for instance, the shear panels are planar.

[0011] still further in accordance with the first aspect, for instance, four of the shear panels are provided, wherein opposite ones of the shear panels are parallel to one another.

[0012] still further in accordance with the first aspect, for instance, planes of the shear panels are tangentially oriented relative to a circle centered about an axis of rotation of the robotic arm actuator and passing through a center of each of the shear panels.

[0013] still further in accordance with the first aspect, for instance, the segment between the motor and the link defines an annular gap relative to adjacent annular segments of the casing shell.

[0014] still further in accordance with the first aspect, for instance, the casing shell has a monoblock body including the segment and the annular segments.

[0015] still further in accordance with the first aspect, for instance, an annular support is positioned between the casing shell and the motor to support the motor.

[0016] still further in accordance with the first aspect, for instance, the motor is positioned between axial planes to which a vector of a rotational axis of the motor is normal, and wherein the shear panels are between the axial planes.

[0017] still further in accordance with the first aspect, for instance, the sensors are strain gauges, the strain gauges being interconnected by a flexible PCB.

[0018] still further in accordance with the first aspect, for instance, a controller PCB may be wired to the flexible PCB and supported by the casing shell.

[0019] still further in accordance with the first aspect, for instance, the casing shell is part of the stator assembly.

[0020] still further in accordance with the first aspect, for instance, the load path is seal-less between the motor and the shear panels.

[0021] in accordance with a second aspect of the present disclosure, there is provided a robotic arm comprising: at least a pair of links; and the robotic arm actuator accordingto the first aspect; wherein the robotic arm actuator provides and actuates a rotational degree of freedom between the pair of links.

[0022] In accordance with a third aspect of the present disclosure, there is provided a torque sensor assembly for a robotic arm actuator, comprising: a casing shell as part of a stator assembly, the shell forming an outer housing for a rotational mechanism; shear panels integrated into the casing shell, configured to isolate on-axis torque from bending moments and axial forces, thereby enhancing torque measurement accuracy; strain gauges positioned on the shear panels to detect and transmit measurements of the on-axis torque; and a printed circuit board connected to the strain gauges via a flexible circuit, facilitating the integration of measurement and control systems.

[0023] Further in accordance with the third aspect, for instance, the shear panels are designed to deform under on-axis torque, isolating the impact of external forces not aligned with the rotational axis.

[0024] Still further in accordance with the third aspect, for instance, the casing shell with shear panels is configured as a monolithic structure, enhancing structural integrity and measurement reliability.

[0025] Still further in accordance with the third aspect, for instance, the shear panels are flat, allowing for easy attachment of strain gauges and minimizing potential measurement errors.

[0026] Still further in accordance with the third aspect, for instance, the printed circuit board is rigid, mounted proximate to the torque sensor assembly, and processes signals from the strain gauges to determine torque values.

[0027] Still further in accordance with the third aspect, for instance, is a redundant set of strain gauges configured in a Wheatstone bridge, providing enhanced reliability and noise reduction in torque measurements.

[0028] Still further in accordance with the third aspect, for instance, the flexible circuit extending from the strain gauges to the printed circuit board is designed to withstand flexing and vibration without signal degradation.

[0029] Still further in accordance with the third aspect, for instance, the shear panels are connected via legs shaped and positioned to direct forces toward the strain gauges, ensuring accurate torque detection.

[0030] Still further in accordance with the third aspect, for instance, seals are positioned between the casing shell and adjacent components to prevent external contamination from affecting sensor accuracy.

[0031] Still further in accordance with the third aspect, for instance, the sensor assembly is capable of differentiating between forces acting along the rotational axis and off-axis forces, providing a higher fidelity measurement of effective torque.

[0032] In accordance with a fourth aspect of the present disclosure, there is provided a robotic arm comprising: at least one link including a robotic arm actuator as described in the third aspect; a torque sensor assembly integrated within the robotic arm actuator, enabling precise control and feedback during robotic operations.

[0033] Further in accordance with the fourth aspect, for instance, the actuator includes a stator and rotor assembly, with the torque sensor assembly located on the stator to measure torque generated by the rotor.

[0034] Still further in accordance with the fourth aspect, for instance, electronic components may be concealed within the links, with the torque sensor assembly providing data for real-time operational adjustments.

[0035] Still further in accordance with the fourth aspect, for instance, a communication interface may be provided for transmitting torque data to a central control unit, enhancing the ability to perform complex tasks.

[0036] Still further in accordance with the fourth aspect, for instance, configured for use in a variety of applications, including manufacturing, servicing, and assistive robotics, benefiting from the enhanced torque measurement provided by the integrated torque sensor assemblies.

[0037] The individual features of the torque sensor assembly of the third aspect may be present individually or in combination with any one of more of the features of robotic arm actuator of the first aspect.DESCRIPTION OF THE DRAWINGS

[0001] Fig. 1 is a perspective view of an articulated robot arm with an isolated torque sensor assembly in actuators thereof, in accordance with the present disclosure;

[0002] Fig. 2 is an elevation view of a robotic arm actuator with isolated torque sensor in accordance with the present disclosure;

[0003] Fig. 3 is a cross-sectional view of the robotic arm actuator of Fig. 2, taken along section line Ill-Ill of Fig. 2;

[0004] Fig. 4 is an exploded view of the robotic arm actuator of Fig. 2;

[0005] Fig. 5 is an exploded view of part of a stator assembly of the robotic arm actuator of Fig. 2, showing a torque sensor assembly;

[0006] Fig. 6 is another exploded view of part of the stator assembly of the robotic arm actuator of Fig. 2, showing a torque sensor assembly;

[0007] Fig. 7 is a side view of a shell of the stator assembly with the torque sensor assembly;

[0008] Fig. 8 is an enlarged view showing details of the torque sensor assembly;

[0009] Fig. 9 is an exemplary side view of the shell of Fig. 7, showing a stress distribution; and

[0010] Fig. 10 is a cross-sectional view of the robotic arm actuator of Fig. 2, showing load paths on the torque sensor assembly.DETAILED DESCRIPTION

[0011] Referring to the drawings and more particularly to Fig. 1 , a mechanism such as a robot arm is generally shown at 10, that may include a torque sensor assembly in accordance with the present disclosure, as shown in subsequent figures. Although the torque sensor assembly is herein described in the context of the robot arm 10, it may be used with other mechanisms, such as articulated mechanisms, or like mechanisms. However, for simplicity, the expression “robot arm” is used throughout, but in a nonlimiting manner. The present disclosure pertains to a torque sensor assembly that may be part of the robot arm 10, or like mechanism. While reference is made to torque sensor, the sensor assembly may also be said to measure forces, and thus may be referred to asa force sensor, as it may be possible to isolate a force value (e.g., in Newtons) from the sensor assembly described herein. Accordingly, the torque sensor assembly may be referred to as a force sensor assembly. The robot arm 10 is a serial articulated robot arm, having a working end 11 and a base end 12. The working end 11 is configured to receive an end effector that may be any appropriate tool, such as gripping mechanism or gripper, anamorphic hand, and tooling heads such as drills, saws, etc. The end effector secured to the working end 11 is as a function of the contemplated use. However, the robot arm 10 is shown without any such tool in Fig. 1 . The base end 12 is configured to be connected to any appropriate structure or mechanism. The base end 12 may be actuated and may or may not be rotatably mounted to the structure or mechanism. By way of non-exhaustive example, the base end 12 may be mounted to a wheelchair, to a vehicle, to a frame, to a cart, to a robot docking station. Although a serial robot arm is shown the joint arrangement of the robot arm 10 may be found in other types of robots, included parallel manipulators.

[0012] The robot arm 10 has a series of links 20 (also known as shells), interconnected by robotic arm actuators 30 (also known as motorized joint units), schematically shown in Fig. 1. Links 20 are the rigid structural components (like bones) that form the body of a robot, while the robotic arm actuators 30 are the joints that are the movable connections (like elbows or shoulders) between the links 20 so as to enable articulation and movement. Together, links and joints form a kinematic chain, determining the robot arm 10's range of motion and dexterity, with joints providing degrees of freedom. The links 20 define the majority of the outer surface of the robot arm 10, but could be concealed under non-structural skins. The links 20 also have a structural function in that they form the skeleton of the robot arm 10 (i.e., an outer shell skeleton), by supporting the robotic arm actuators 30 and tools at the working end 11 , with loads supported by the tools, in addition to supporting the weight of the robot arm 10 itself. Wires and electronic components may be concealed into the links 20, by internal routing, although this is optional. Caps 21 may be provided in the links 20 to provide an access to the robotic arm actuators 30, for assembling and disassembling the robot arm 10, etc.

[0013] The links 20 may be defined by a tubular body. An outer peripheral surface of the tubular bodies forms the majority of the exposed surface of the robot arm 10 but the tubular bodies could be concealed under non-structural skins, and / or the links 20 couldhave other configurations than a tubular body as a possibility. The tubular bodies may differ in length, in diametrical dimension, and in shape. For example, as shown in Fig. 1 , some of the links 20 may be generally straight or angled, i.e., arranged such that the rotation angles of the robotic arm actuators 30 at their opposed ends are parallel, perpendicular, or at any other angle. Some links 20 may be longer, etc. Also, although the open ends of the tubular bodies of the links 20 may have the same diameter for all robotic arm actuators 30 to be the same size, it is contemplated to scale down the robotic arm actuators 30 from the proximal base end 12 to the distal working end 11 to reduce the overall weight of the robot arm 10. In such a case, the diameter of the open ends of the links 20 may incrementally reduce toward the distal end. The tubular bodies of the links 20 may consist of any appropriate material, including composites, plastics, metals, or any combination thereof. The tubular bodies may be monolithic pieces, or an assembly of components, and may be molded, extruded, machined, etc.

[0014] The robotic arm actuators 30 interconnect adjacent links 20, in such a way that a rotational degree of actuation is provided between adjacent links 20. According to an embodiment, the robotic arm actuators 30 may also connect a link 20 to a tool at the working end 11 (e.g., via wrist device), or to a base at the base end 12, although other mechanisms may be used at the working end 11 and at the base end 12. The robotic arm actuators 30 may also form part of structure of the robot arm 10, as they interconnect adjacent links 20.

[0015] The motorized joint unit 30 is of the type having a stator assembly 40, a rotor assembly 50 rotatable relative to the stator assembly 40 along rotational axis X, as a response to actuation from the motorization components inside the motorized joint unit 30. Reverse arrangements of the stator assembly 40 and rotor assembly 50 are possible. A torque sensor assembly 60 is mounted to the stator assembly 40.

[0016] Referring to Fig. 2, the stator assembly 40 has a casing shell 41 , also referred to as a casing, as a shell, as a housing. The casing shell 41 forms part of the structure of the stator assembly 40, as it is via the casing shell 41 that the stator assembly 40 is connected to one of the links 20. The casing shell 41 may be secured in any appropriate mannerto the tubular body of the link 20. Other arrangements are possible, with the shell 41 integrating or being the link 20. Referring to Fig. 7, an outer surface of the casing shell41 sequentially defines a connection segment 41 A, a sensor supporting segment 41 B, a sealing segment 41 C, and a support segment 41 D. More orfewer of such segments may be present, and the arrangement and present description of four segments is only a manner to describe parts of the casing shell 41.

[0017] The connection segment 41A has an annular contact surface 41A1 with a plurality of connection holes, for connection of a tubular link 20 to the stator assembly 40, as one possible way to secure the stator assembly 40 to the tubular link 20. Other configurations are possible. As shown in Fig. 2, a shoulder 41 A2 tapers toward another tubular section 41A3. The tubular section 41A3 may be used to support some components of the torque sensor assembly, as detailed hereinafter. For example, posts 41 A4 (Fig. 3) may be present, and may feature threaded holes, as one possibility.

[0018] The sensor supporting segment 41 B exhibits a reduction in diametrical dimensions, forming an annular gap or channel, and is configured to support the torque sensor assembly 60. Hence, the torque sensor assembly 60 measures deformation at the sensor support segment 41 B. The sensor supporting segment 41 B is further detailed below.

[0019] The sealing segment 41 C defines one or more annular channel(s) for receiving a seal or seal(s) that will serve as a barrier between the tubular link 20 positioned over the casing shell 41 , and the casing shell 41 , or as a barrier between the casing shell 41 and a shell of the rotor assembly 50 (Fig. 3). As an alternative to seals, tight fits could suffice in forming the barrier, i.e. no seals.

[0020] The support segment 41 D may have different sections of different diameters, and is rotatably coupled to the rotor assembly 50, to act as a support for the rotor assembly 50 during rotation of the latter.

[0021] A support 42 is located inside the casing shell 41. The support 42 may also form part of the structure of the stator assembly 40, as components inside the motorized joint unit 30 are supported by the support 42 as described hereinafter. The support 42 may be a drum-like feature, that is held against an inner surface of the casing shell 41 , via a first tubular portion thereof, shown as 42A. As observed from Fig. 3, the support 42 abuts against the sealing segment 41 C, as an example among others. The support 42 could be aligned with other parts of the casing shell 41. Another tubular portion 42B maybe connected to an end of the tubular portion 42A, and may have a smaller diameter. However, this is optional. The tubular portion 42B may be cylindrical as shown, frusto-conical, etc. In an embodiment, the tubular portion 42B is concentric with the outer wall of the casing shell 41 , relative to axis X, though this is an option. In another embodiment, the casing shell 41 is monolithic with the support 42 but other attachment arrangements are possible.

[0022] An annular receptacle may consequently be defined by an inner surface of the support 42. The annular receptacle receives therein the motor 43 that imparts a rotation to the rotor assembly 50. The motor 43 is schematically shown, as it may be any appropriate type of actuator, including a bi-directional electric motor, a pneumatic or hydraulic actuator, etc, and possibly a brake system described in United States Patent No. 10,576,644. The motor 43 may for example include a stator core 43A with windings thereon, according to an embodiment. The motor 43 may have a part thereof secured to the stator assembly 40, another part thereof secured to the rotor assembly 50. Accordingly, the motor 43 may be said to be part of the stator assembly 40 and / or part of the rotor assembly 50, and / or between the stator assembly 40 and the rotor assembly 50. However, for simplicity, the windings and stator core are not shown in the figures. The stator core 43A may be secured to the support 42. The motor 43 may further include an internal rotor 43B for example constituted of a plurality of permanent magnets, supported by a ring. For simplicity, the permanent magnets and the ring are not shown in the detail in the figures. The electric motor 43, or like actuator, is operated to provide the desired rotation between adjacent links 20, for example in terms of speed and torque, relative to axis X. The motor 43 or like actuator is configured for reciprocating movement (i.e., clockwise and counterclockwise), and low frequency movements, for some implementations of the robot arm 10. Non exhaustive or limitative rotor / stator kits that may be used include an external rotor motor (e.g., brushless), axial flux or pancake-type motor (brushed, brushless or stepper), internal rotor motors with hollow rotor. The annular receptacle of the support 42 is one contemplated solution to secure the stator of the motor 43 to the structural components of the stator assembly 40. For example, the stator of the motor 43 may be fixed directly to an inner wall of the casing shell 41.

[0023] It can be observed that the motor 43 is located between a pair of axial planes, shown as P1 and P2. An axial plane can be defined as a plane to which a vector of the rotational axis X is normal.

[0024] In an embodiment, bearing or bearing assemblies are generically shown as 44A, 44B, etc, and referred to herein as 44. The bearing assemblies 44 are the part of the stator assembly 40 rotatingly supporting the rotor assembly 50, such that the rotor assembly 50 may rotate about the stator assembly 40 as a result of actuation input from the motor 43. For simplicity, the bearing assemblies 44 are shown in Fig. 3 as ball bearings, but other types of bearings could be used. A separation between the stator assembly 40 and the rotor assembly 50 is shown as SL in Fig. 3, and is indicative of what rotates relative to what is static when the motor 43 imparts a rotation of the rotor assembly 50. The separation SL is shown in a top half of Fig. 3, with a mirror separation present in the bottom half of Fig. 3, but not shown.

[0025] Other components may optionally be part of the stator assembly 40, as shown as 45 and 46 and 47. Item 45 may be a stator part of a speed reduction mechanism, optionally present to reduce the reduction of speed between rotor and stator. Item 46 may be a brake assembly that may include a brake coil and brake. Items 45 and 46 are representative of components that may or may not be in the robot arm 10.

[0026] The rotor assembly 50 is shown in a simplified configuration, with a shaft 51 upon which is mounted the rotor 43B of the motor 43. Thus, actuation of the motor 43 causes a rotation of the shaft 51 . The shaft 51 is rotatably connected to the stator assembly 40, for instance by the bearing assemblies 44 rotatably supporting the shaft 51 such that the shaft 51 may rotate about axis X. The bearing assemblies 44 supporting the shaft 51 are illustrated as 44A in Fig. 3, and are mounted to a tubular member 52. The tubular member 52 is part of the rotor assembly 50, but may not rotate at the same speed as the shaft 51 , because of the presence of a reduction mechanism 53 coupled to the shaft 51 , and causing a speed reduction via a support 54, to which is connected a casing shell 55 of the rotor assembly 50. A coupling disk 56 is secured to the casing shell 55 and supports the tubular member 52.

[0027] The tubular member 52 may therefore define a canal through which power and / or telecommunication wires may be passed. In a serial arm such as the robot arm 10, the presence of a canal may allow internal routing of all cables.

[0028] Referring to Figs. 2, 3 and 4, an outer surface of the casing shell 55 may define a connection segment 55A, and sealing segment 55B. More or fewer of such segments may be present, and the arrangement of foursegments is only a mannerto describe parts of the casing shell 55.

[0029] The connection segment 55A has an annular contact surface 55A1 with a plurality of connection holes, for connection of a tubular link 20 to the rotor assembly 50, as one possible way to secure the rotor assembly 50 to the tubular link 20. Other configurations are possible.

[0030] The sealing segment 55B defines one or more annular channel(s) for receiving a seal or seal(s) that will serve as a barrier between the tubular link 20 positioned over the casing shell 55, and the casing shell 55. As an alternative to seals, tight fits could suffice in forming the barrier. Seals are generally shown as S in the figures.

[0031] One of the bearing assemblies 44, shown as bearing assembly 44B in Fig. 3, is positioned between the casing shells 41 and 55. The bearing assembly 44B is received in a counterbore within the inner cavity of the casing shell 55.

[0032] The above arrangement is provided as an example only, as a reverse arrangement is contemplated as well, for instance with a motor having an inner rotor / outer stator configuration. The rotor assembly 50 may have fewer or more than the components shown.

[0033] Now that an exemplary configuration has been described, the present disclosure provides more details on the torque sensor assembly.

[0034] Referring to Figs. 2 to 9, the torque sensor assembly is generally shown at 60 in varying levels of details. The torque sensor assembly 60 may be used to measure torques in the robot arm 10, such as forces between adjacent links 20, at the robotic arm actuator 30. In an embodiment, the torque sensor assembly 60 is used to produce torque data, etc. For simplicity, the expression used herein is “torque sensor”, but the torque sensor assembly 60 may produce other force-related data in other forms, with suitablecalculations. Therefore, the use of the expression “torque sensor assembly” herein is not intended to limit the capacity of the sensor assembly shown. The torque sensor assembly 60 may be said to be integrated, in that sensing components are positioned in part of the structure of the stator assembly 40, such as in the casing shell 41. Stated differently, the sensor assembly 60 has its sensing components directly on a main body part of the stator assembly 40, such that load paths extend through the part of the stator assembly 40 where the sensing components are. As a result, the torque sensor assembly 60 may have the capacity to provide torque readings that are more complete and inclusive of the various torques present at the joint between links 20.

[0035] The torque sensor assembly 60 has sensors therefore located in the gap defined radially outwardly in the sensor supporting segment 41 B of the casing shell 41. It can be observed that the sensor supporting segment 41 B is located axially between the axial planes P1 and P2, as may be a substantial portion of the support 42. Therefore, the sensor supporting segment 41 B is in close proximity to the motor 43.

[0036] The sensor supporting segment 41 B may have a particular structural configuration to be suited to monitor the torque. More particularly, the sensor supporting segment 41 B has a plurality of shear panels 410, one of which is shown clearly in Fig. 9. The shear panels 410 are flat in a variant. The shear panels 410 may have a pair of side edges 411. The side edges 411 may be parallel to the axial planes P1 and P2. In a variant, a plane of one or more of the shear panels 410 is in a tangential orientation at its center relative to a virtual circle whose center is coincident with rotational axis X (Fig. 3). In a variant, a plane of all of the shear panels 410 is in a tangential orientation at its center relative to a virtual circle whose center is coincident with rotational axis X (Fig. 3).

[0037] The shear panels 410 may be supported by legs 412, and ends thereof. For example, as seen in Fig. 9, there may be a pair of legs 412 at the two ends of the shear panels 410. The legs 412 may be an extension of the side edges 411 , i.e., an edge of the legs 412 may form a continuous edge with respective ones of the side edges 411. In a variant, the entire sensor support segment 41 B is made of a monoblock of material (or an integral piece of material), and the geometry of the sensor support segment 41 B is machined or cast. In another variant, the entire casing shell 41 has a monoblock body, including the sensor support segment 41 B. In a variant, the casing shell 41 is made of ametal. This is optional however. Therefore, the shear panels 410 and the legs 412 may be the result of a pair of cutouts 413, and a pair of bores 414. The cutouts 413 may be obround slots, as a possibility, as shown in Fig. 9. The bore 414 may define a taper in a direction of the shear panels 410, to increase the sensitivity of the shear panels 410 to shear forces.

[0038] As observed from Figs. 2-9, there may be four shear panels 410, although there may be more or fewer. In a variant with four shear panels 410, the shear panels 410 that are on opposite sides of the central axis X may be parallel to one another. The shear panels 410 may be connected to a remainder of the casing shell 41 by webs 415. The webs 415, that may or may not be part of a monoblock with the sheer panels 410. The webs 415 may be rounded or flat, or have a planar portion. If a planar portion is present in the webs 415, a plane may be in a tangential orientation at its center relative to a virtual circle whose center is coincident with rotational axis X (Fig. 3). The plane of any one of the webs 415 may be at 45 degrees relative to a plane of the adjacent shear panels 410, as an option. The webs 415 may further include a cutout 416, to direct forces toward the shear panels 410. The webs 415 extend end to end between the adjacent segments of the casing shell 41 .

[0039] The torque sensor assembly 60 features one or more strain gauges 61 as one possible type of torque sensorthat may be used. In the illustrated embodiment, there are four strain gauges 61 , i.e., one on each of the shear panels 410, but this is optional. The strain gauges 61 may be arranged in a Wheatstone bridge, as a possibility.

[0040] In an embodiment, a flexible printed-circuit board (PCB) 62 extends from strain gauge 61 to strain gauge 61. The flexible PCB 62 may have a ribbon body, that is elongated, and that may extend along the outer surface ofthe sensor supporting segment 41 B, in the gap it defines in the casing shell 41. The PCB 62 may further include a tab 62A, for electronic connection to a rigid PCB 63, or like card member or card. The PCB 63 may be said to be the controller of the robotic arm actuator 30, or part thereof. Referring to Fig. 6, an adhesive 64, such as double sided tape as an example among others, may be present to secure the flexible PCB 62 to the casing shell 41. The adhesive 64 may be in the form of a strip, similar to the strip body ofthe PCB 62. The adhesive 64 is optional, or alternatives such as glue, discrete tape segments, mechanical fastenersmay be present. The tab 62A may for example be routed through one of the cutouts 413, or other, to be connected to the PCB 63.

[0041] Alternatively, the strain gauges 61 may be wired to one another and / or to the PCB 63. The optional configuration featuring the flexible PCB 62, which links the strain gages 61 to the main sensing PCB 63, is a compact design. In terms of assembly, it may facilitate soldering and may result in lower noise levels.

[0042] PCB 63, e.g., of the rigid type, may be mounted to posts 41 A4 such that the PCB 63 is in relatively close proximity to the sensor supporting segment 41 B. In a variant, a vector of the rotational axis X is normal to the plane of the PCB 63. The PCB 63 may support the electronic components required for the torque sensor assembly 60 to perform force measurements. Moreover, the PCB 63 may have additional sensors, such as temperature sensors, optical sensors, encoders, etc. The PCB 63 may be the main card to drive the robotic arm actuator 30, through additional PCBs 65 and 66 are shown (Fig. 5).

[0043] Thus, the torque sensor assembly 60 may be said to be assembled on the casing shell 41 , that may be a metallic housing in a variant. The torque sensor assembly 60 is therefore on the input side, the drive side, as opposed to being on the driven side of the robotic arm actuator 30. Moreover, the sensors 61 are on a structural component of the robotic arm actuator 30, as opposed to being on an additional component, to measure deformation of the structural component, i.e., the casing shell 41. The torque sensor assembly 60 may have strain gauges 61 installed and connected to the control boards (e.g., 63, 65, 66) of the robotic arm actuator 30 via the flexible PCB 62 (a.k.a., flex PCB 62). The flexible PCB 62 may be adhered around the strain gauges 61 , such as by double sided tape 64 or equivalent. The torque sensor assembly 60 may be said to be composed of three sub-modules: the housing defined by the sensorsupport segment 41 B (though it is part of the structure of the stator assembly 40), the sensors 61 in the form of a strain gauge assembly, and reading circuits, such as flexible PCB 62 and / or wires. As such, the torque sensor assembly 60 may be said to be fully integrated into the robotic arm actuator 30.

[0044] Because of the configuration described above, the torque sensor assembly 60 may be said to isolate off-axis forces and bending moments, even though off-axis forcesand bending moments cannot be entirely eliminated. The highest ratio of on-axis torque compared to off-axis loads is desired when designing the geometry, but the rigidity of the casing shell 41 in cross-axis may also affect the on-axis torque readings, as well as peak stress. On-axis torque may generally be described as a measure of a rotational force acting directly around a specific axis of rotation (e.g., axis X). The on-axis torque defines how effectively a perpendicular force turns an object, the perpendicular force calculated as the force multiplied by the distance from the pivot (lever arm) or axis of rotation. In contrast, an off-axis load occurs when a force is applied to a component, structure, or sensor at an angle or position that is not aligned with its primary designed axis (axis of rotation X). The strain gauges 61 are positioned to read the internal torques from the motor 41 and various seals. In a robot arm 20 such as in Fig. 2, the robotic arm actuators 30 may be of different sizes. For example, the robotic arm actuator 30 at or nearer to the end effector 11 may be smaller than those at or near the base 12. For example, a single robot arm 10 may have robotic arm actuators 30 that come in different sizes such as 65 mm, 80 mm, 90 mm and 110 mm. The design of the torque sensor assembly 60 is such that the torque sensor assemblies 60 in respective robotic arm actuators 30 may be easily scaled.

[0045] The sensor supporting segment 41 B of the casing shell 41 has the shear panels 410 that isolate bending moments and axial force: the legs 41 connect the shear panels 410 to a remainder of the sensor supporting segment 41 B and deform when a bending moment or axial load is applied, preventing the deformation of the shear panels 410, but not when an on-axis torque is applied.

[0046] Although other sensor arrangements are considered, the use of four strain gauges 61 wired in 2 pairs provides redundancy by enabling the torque sensor assembly 60 to obtain two signals. The isolated readings allow a low enough discrepancy between the two pairs of strain gauges 61 , such that the signals can be compared in real-time to ensure the integrity of output from torque sensor assembly 60. Moreover, the shear forces may be isolated by using the pairs of opposite strain gauges 61 : when a shear force is applied on the torque sensor assembly 60, both strain gauges 61 read opposite to each other, such that the readings can be evened.

[0047] As discussed above, the isolated shear panels 410 may be flat, meaning that the strain gauges 61 can be more easily glued to their respective host surfaces. The positioning of the sensors 61 is such that internal friction is measured by the sensors 61 and the readings can be calibrated based on the internal friction. The use of the isolated shear panels 410 on the input housing, i.e., casing shell 41 , of the actuator 30 allows a more accurate and isolated reading of the on-axis torque without adding length or volume to the actuator 30, such as if a dedicated torque sensor were installed in an isolated position on the actuator 30. The upstream position of the torque sensor assembly 60 relative to the motor 43 may allow a reading of all internal torques, such as from the motor 43 and seals. Stated differently, the torque readings may include all internal torques from the motor 43 and seal friction, such that the readings from the torque sensor assembly 60 have enhanced accuracy, which may result in more accurate control of the robot arm 10, whether in hand guiding collaborative mode or when movement of the robot arm 10 is entirely controlled by its controller.

[0048] Although more sensors 61 could be used, the presence of only four strain gauges 61 may reduce cost, time of assembly, and yield of correctly assembled modules. As a result, the relative simplicity of assembly may allow manufacturing to be carried out by non-specialized technicians. This may be particularly useful for low production volumes. This being said, shorter shear panel 410 may decrease the on-axis to off-axis loads ratio as well as increase the sensitivity to the positioning of the strain gauges 61. The positioning of the strain gauges 61 may be more critical than in “cup” style torque sensors, notably to eliminate static bandwidth. The shear panels 410 are designed so that a peak strain is obtained at a specific location.

[0049] As the sensor supporting segment 41 B has been positioned in the casing shell 41 , notably with a gap or like annular channel relative to a remainder of the outer surface of the casing shell 41 , it may be said that the presence of the torque sensor assembly 60 does not add any volume to the actuator 30. Therefore, in contrast to robotic arm actuators 30 without the configuration described above, the robotic arm actuator 30 of the present disclosure may have a relatively smaller size that may be easier to integrate in the context of a robotic arm.

[0050] The upstream position of the torque sensor assembly 60 relatively to the motor and seals in the arrangement described above allows the torque from the motor, seals, and all other inside frictions to be read by the torque sensor, increasing the accuracy of the torque sensor, and thus the control of the robotic arm. This position is challenging to obtain due to volume and complexity constraints. This challenge is resolved by the arrangement described herein.

[0051] More particularly, Fig. 10 shows a similar view as Fig. 3, but with reference numerals removed for clarity. In Fig. 10, various load paths are illustrated relative to the torque sensor assembly 60, to illustrate the fact that the torque sensor assembly 60 captures torque components present in the actuator 30. The load path of the output shaft and associated components (e.g., clockspring) is generally shown as L1. The motor torque load path is shown as L2. The load path of the reduction mechanism 53 is shown as L3. The load path resulting from friction of the seal(s) between the shells of the links 20 is shown at L4. Accordingly, these results a load path L5 at the torque sensor assembly 60.

[0052] The robotic arm actuator 30 in accordance with the present disclosure may generally be described as having a stator assembly; a rotor assembly; and a motor between the stator assembly and the rotor assembly to impart a relative rotation between the stator assembly and the rotor assembly. The stator assembly or the rotor assembly has a casing shell connected to the motor and configured to be connected to a link, the casing shell defining a plurality of shear panels in a segment between the motor and the link for the plurality of the shear panels to be in a load path therebetween, and sensors on the shear panels configured to measure torque on the shear panels. In a variant, the combination of the sensors and the shear panels may be described as a torque sensor assembly. The torque sensor assembly may optionally be described as including the casing shell as part of a stator assembly, the shell forming an outer housing for a rotational mechanism, shear panels integrated into the casing shell, configured to isolate on-axis torque from bending moments and axial forces, thereby enhancing torque measurement accuracy, strain gauges positioned on the shear panels to detect and transmit measurements of the on-axis torque, and a printed circuit board connected to the strain gauges via a flexible circuit, facilitating the integration of measurement andcontrol systems. In an optional variant, the shear panels are designed to deform under on-axis torque, isolating the impact of external forces not aligned with the rotational axis. In an optional variant, the casing shell with shear panels is configured as a monolithic structure, enhancing structural integrity and measurement reliability. In an optional variant, the shear panels are flat, allowing for easy attachment of strain gauges and minimizing potential measurement errors. In an optional variant, the printed circuit board is rigid, mounted proximate to the torque sensor assembly, and processes signals from the strain gauges to determine torque values. In an optional variant, there is a redundant set of strain gauges configured in a Wheatstone bridge, providing enhanced reliability and noise reduction in torque measurements. In an optional variant, the flexible circuit extending from the strain gauges to the printed circuit board is designed to withstand flexing and vibration without signal degradation. In an optional variant, the shear panels are connected via legs shaped and positioned to direct forces toward the strain gauges, ensuring accurate torque detection. In another optional variant, seals are positioned between the casing shell and adjacent components to prevent external contamination from affecting sensor accuracy. In an optional variant, the sensor assembly is capable of differentiating between forces acting along the rotational axis and off-axis forces, providing a higher fidelity measurement of effective torque.

Claims

CLAIMS:

1. A robotic arm actuator comprising:a stator assembly;a rotor assembly; anda motor between the stator assembly and the rotor assembly to impart a relative rotation between the stator assembly and the rotor assembly;wherein the stator assembly or the rotor assembly hasa casing shell connected to the motor and configured to be connected to a link, the casing shell defining a plurality of shear panels in a segment between the motor and the link for the plurality of the shear panels to be in a load path therebetween, andsensors on the shear panels configured to measure torque on the shear panels.

2. The robotic arm actuator according to claim 1 , wherein the shear panels are planar.

3. The robotic arm actuator according to claim 2, including four of the shear panels, wherein opposite ones of the shear panels are parallel to one another.

4. The robotic arm actuator according to claim 3, wherein planes of the shear panels are tangentially oriented relative to a circle centered about an axis of rotation of the robotic arm actuator and passing through a center of each of the shear panels.

5. The robotic arm actuator according to any one of claims 1 to 4, wherein the segment between the motor and the link defines an annular gap relative to adjacent annular segments of the casing shell.

6. The robotic arm actuator according to claim 5, wherein the casing shell has a monoblock body including the segment and the annular segments.

7. The robotic arm actuator according to any one of claims 1 to 6, wherein an annular support is positioned between the casing shell and the motor to support the motor.

8. The robotic arm actuator according to any one of claims 1 to 7, wherein the motor is positioned between axial planes to which a vector of a rotational axis of the motor is normal, and wherein the shear panels are between the axial planes.

9. The robotic arm actuator according to any one of claims 1 to 8, wherein the sensors are strain gauges, the strain gauges being interconnected by a flexible PCB.

10. The robotic arm actuator according to claim 9, further including a controller PCB wired to the flexible PCB and supported by the casing shell.

11. The robotic arm actuator according to any one of claims 1 to 10, wherein the casing shell is part of the stator assembly.

12. The robotic arm actuator according to any one of claimsl to 11, wherein the load path is seal-less between the motor and the shear panels.

13. A robotic arm comprising:at least a pair of links; andthe robotic arm actuator according to any one of claims 1 to 12;wherein the robotic arm actuator provides and actuates a rotational degree of freedom between the pair of links.

14. A torque sensor assembly for a robotic arm actuator, comprising:a casing shell as part of a stator assembly, the shell forming an outer housing for a rotational mechanism;shear panels integrated into the casing shell, configured to isolate on-axis torque from bending moments and axial forces, thereby enhancing torque measurement accuracy;strain gauges positioned on the shear panels to detect and transmit measurements of the on-axis torque; anda printed circuit board connected to the strain gauges via a flexible circuit, facilitating the integration of measurement and control systems.

15. The torque sensor assembly according to claim 14, wherein the shear panels are designed to deform under on-axis torque, isolating the impact of external forces not aligned with the rotational axis.

16. The torque sensor assembly according to claim 14 or claim 15, wherein the casing shell with shear panels is configured as a monolithic structure, enhancing structural integrity and measurement reliability.

17. The torque sensor assembly according to any one of claims 14 to 16, wherein the shear panels are flat, allowing for easy attachment of strain gauges and minimizing potential measurement errors.

18. The torque sensor assembly according to any one of claims 14 to 17, wherein the printed circuit board is rigid, mounted proximate to the torque sensor assembly, and processes signals from the strain gauges to determine torque values.

19. The torque sensor assembly according to any one of claims 14 to 18, including a redundant set of strain gauges configured in a Wheatstone bridge, providing enhanced reliability and noise reduction in torque measurements.

20. The torque sensor assembly according to any one of claims 14 to 19, wherein the flexible circuit extending from the strain gauges to the printed circuit board is designed to withstand flexing and vibration without signal degradation.

21. The torque sensor assembly according to any one of claims 14 to 20, wherein the shear panels are connected via legs shaped and positioned to direct forces toward the strain gauges, ensuring accurate torque detection.

22. The torque sensor assembly according to any one of claims 14 to 21, further comprising seals positioned between the casing shell and adjacent components to prevent external contamination from affecting sensor accuracy.

23. The torque sensor assembly according to any one of claims 14 to 22, wherein the sensor assembly is capable of differentiating between forces acting along the rotational axis and off-axis forces, providing a higher fidelity measurement of effective torque.

24. A robotic arm comprising:at least one link including a robotic arm actuator as described in any one of claims 14 to 23;a torque sensor assembly integrated within the robotic arm actuator, enabling precise control and feedback during robotic operations.

25. The robotic arm according to claim 24, wherein the actuator includes a stator and rotor assembly, with the torque sensor assembly located on the stator to measure torque generated by the rotor.

26. The robotic arm according to claim 24 or claim 25, further comprising electronic components concealed within the links, with the torque sensor assembly providing data for real-time operational adjustments.

27. The robotic arm according to any one of claims 24 to 26, incorporating a communication interface for transmitting torque data to a central control unit, enhancing the ability to perform complex tasks.

28. The robotic arm according to any one of claims 24 to 27, configured for use in a variety of applications, including manufacturing, servicing, and assistive robotics, benefiting from the enhanced torque measurement provided by the integrated torque sensor assemblies.

Images